This application claims the priority of German Application No. 197 21 750.8, filed May 24, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process for detecting and reporting traffic situation data of a road system by means of sample vehicles, in which case, according to the process, in the respective sample vehicle, at predeterminable points in time, an automatic position determination is carried out and pertaining traffic situation data are detected and reported as a function thereof.
Conventionally, traffic situation data, for example, for an automobile road system, are determined based on the infrastructure. As an example, the traffic situation data are determined by measuring instruments in the form of induction loops along the observed road system and are transmitted by way of signal cables to a central information center where they are analyzed by means of special hardware and software and in the process are examined particularly with respect to occurred traffic disturbances. These infrastructure-supported processes require comparatively high expenditures and, in addition, do not permit the recognition of disturbances before their effects are exhibited at at least one measuring point of the road system.
For improving this conventional approach, processes of the above-mentioned type are known which do not require a route-side infrastructure in that the detection and reporting of the traffic situation data is carried out by so-called sample vehicles, also known as "floating cars" which are equipped for this purpose and drive in the considered road system. The term "sample vehicle" has the purpose of expressing that it is sufficient to lay out a comparatively small proportion of all vehicles using the road system in this manner as such sample vehicles for obtaining the traffic situation data, that is, route-related data relevant to assessing the traffic situation in the respective road system. The reporting of the traffic situation data preferably takes place by way of a radio communication path, such as a mobile radio network, to a stationary center and/or other vehicles. A known difficulty of these processes is the fact that the data quantity normally transmitted during each traffic situation data reporting operation is relatively large with respect to the capacity of existing radio networks so that an overloading of the radio networks may occur. In addition, the processing of the large amounts of data requires correspondingly high computing expenditures.
In order to remedy this situation, a process of the above-mentioned type is suggested in German Published Patent Application DE 195 21 919 A1 in the case of which the data quantity to be transmitted is reduced by the fact that the traffic-situation-relevant vehicle and position data detected by the respective sample vehicle are assigned to one or several vehicle and position data classes which correspond to a defined typical vehicle handling, and the assigned class is transmitted as an actual vehicle handling pattern with the position data in the case of a respective reporting operation, especially to a traffic computer. As a result, it is to be achieved that, during a respective reporting operation, the complete data sets of the vehicle data and position data must not be transmitted but only the assigned vehicle handling pattern in the form of an identification which indicates the momentary classification, together with the position data of the sample vehicle.
Another process for determining traffic situation data by means of a sample vehicle fleet with data-quantity-reducing measures is described in German Published Patent Application DE 195 17 309 A1. In the case of this process, the vehicles are divided into exchange groups, in which vehicles of a respective exchange group exchange vehicle data among one another, that is, data concerning the environmental and/or operating condition of the vehicle, and position data; that is, data concerning the position of the respective vehicle at a respective point in time. A selected vehicle of each exchange group transmits the processed vehicle and position data of an exchange group to a central computer, the position data being transmitted periodically after a certain route distance was covered and/or after the expiration of a given time period. For the vehicle data, it can be provided that tolerance values are defined and these are transmitted together with the position data only when a portion of the tolerance values exceed the defined tolerance values.
The invention is based on the technical problem of providing a process of the above-mentioned type by which traffic situation data can be obtained in a reliable manner and at relatively low cost.
The invention achieves this object by providing a process in which the observed road system is stored in the sample vehicles together with the drive duration data concerning the drive duration to be expected for the partial routes of the road system, for example, as digital data, in an electronic memory. After a respective automatic position determination which can be triggered, for example, at defined time intervals or when certain locations of the road system are reached, or when one or several other defined triggering criteria occur, the determined actual position is compared with the position to be expected by means of the stored partial route drive duration data and/or the actual drive duration is compared with the drive duration to be expected by means of the stored partial route drive duration data. The actual drive duration is determined as the time period between the actual and the preceding position determination operation, while the drive duration to be expected can be read directly from the stored drive duration data. Based on the vehicle position known from the preceding position determination operation, the position to be expected is determined in that the point of the subsequently driven partial route of the road system is found by means of the stored road system for which the stored drive duration to be expected corresponds to the time period until the actual position determination operation. Subsequently, a traffic situation data reporting operation will only be triggered if the actual position and/or drive duration deviates by more than a respective definable threshold value from the expected position or drive duration.
Thus, in the case of this process, traffic situation reporting operations do not take place as long as the sample vehicle moves with a tolerance definable by the threshold value within the scope of the drive duration data stored for the individual partial routes of the road system. Expediently, the stored partial route drive duration data correspond to a traffic situation with no disturbances. The absence of traffic situation data reporting operations by a respective sample vehicle is therefore an indication of a traffic situation without disturbances for a possible center and/or for the other vehicles driving in the road system. The transmission of route-related data from a respective sample vehicle in situations without any traffic disturbances, which is unnecessary for recognizing traffic disturbances, is avoided by means of this process, which, on the whole, considerably reduces the amounts of data to be transmitted so that the data communication can take place without any problem on a conventional mobile communication path, such as a digital radio telephone network. If a traffic disturbance, such as a traffic backup, occurs on a partial route travelled by a sample vehicle, this will be reliably recognized during a next position determination of that vehicle in that a significant deviation is recognized of the actual position from the position to be expected according to the stored partial route drive duration data or a correspondingly significant deviation is recognized of the drive duration required for reaching a certain route point from the drive duration to be expected according to the stored drive duration data. This will then, possibly linked to additional triggering conditions, lead to the triggering of a corresponding report of the actual traffic situation data which characterize the traffic situation, that is, the traffic disturbance, deviating from the stored expected traffic situation.
In the case of a process further described herein, the stored drive duration to be expected for the individual partial routes of the road system is not fixedly defined but is defined as a variable which depends at least on the time-of-day and/or the date. As a result, the fact can be taken into account in a simple manner that different drive durations must be expected at least on certain partial routes at certain times-of-day because of a traffic density and/or road condition which fluctuates as a function of the time-of-day, the day of the week and/or the season.
In the case of a process further described herein, the threshold value for the determined position deviations or drive duration variations is not unchangeable but is defined as a variable which depends at least on the variance of the vehicle speed. As a result, different driving conditions can be taken into account in a relatively simple manner. For example, in the case of a typically more fluctuating vehicle speed, a traffic situation data reporting operation is triggered only in the case of a larger deviation of the actual position or drive duration from the position or drive duration to be expected than in the case of lower speed fluctuations. By a correspondingly variable selection of the threshold value, systematic deviations can also be taken into account which may, for example, be based on the fact that for a faster driver drive durations may occur which have the tendency to be shorter than the drive durations to be expected, and vice-versa, for a more careful driver, drive durations may occur which are longer than the drive durations to be expected.
In the case of a process further described herein, reported traffic situation data which point to a certain traffic disturbance are interpreted by a receiving center or by other vehicles as an actual traffic disturbance only if several situation data reports which correspond to one another in this respect are received from the sample vehicle or vehicles within a definable confirmation period. This provides protection against accidental erroneous reports or incorrect traffic disturbance reports by an atypically driven sample vehicle.
In the case of a process further described herein, it is provided that, in the event of the presence of a constant deviation of the actual drive duration from the drive duration to be expected for a definable longer observation period, the actual drive duration for the respective partial route of the road system is stored as a new driving duration to be expected for all vehicles. In addition, in this manner, a drive duration can be stored for the first time for partial routes of the road system for which so far no drive duration to be expected has been available. Also, optionally new partial routes which so far have not been a component of the stored road system can be detected during the first drive by a sample vehicle on these partial routes and can be stored for the first time together with the required drive duration as the drive duration to be expected which correspondingly expands the stored road system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.